Hose for drip irrigation and method of producing same

ABSTRACT

The irrigation hose comprises two tubes disposed one within the other, at least one of the tubes being grooved. The ungrooved tube forms with the groove or grooves of the other tube continuous secondary ducts over the entire length of the hose. Inlet ports and outlet ports delimit in the secondary ducts sections of a predetermined length, each yielding a flow capable of continuously drip-irrigating a plant in the area to be irrigated. The outlet ports and the inlet ports are distributed along spiral lines if the secondary ducts are straight and along straight lines constituting generatrices of the hose if the secondary ducts run along spirals.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to irrigation equipment, and more particularly toa hose for drip or trickle irrigation, of the type having a primary ductof large cross-section, at least one secondary duct of smallcross-section, and inlet and outlet ports causing the primary duct tocommunicate with each secondary duct, on the one hand, and the latter tocommunicate with the outside, on the other hand. The invention furtherrelates to a method and an installation for producing such a hose.

Drip irrigation is a method of cultivation which is finding increasinglywidespread application in countries desirous of boosting theiragricultural or horticultural output. In this method, specially designedhoses are placed in the cultivated areas in such a way that they can becontinuously supplied with water under pressure and can, in turn, supplya trickle of water at the base of each plant. Hoses must thus be placedalong each row of plants so that a nozzle allowing water to drip out issituated close to each plant. Hence these nozzles must be distributedalong the hoses at distances corresponding to the spacing between theplants. In general, such hoses are of plastic and can thus be wound upon reels or revolving stands when not in use. Some examples of the priorart are found in the published French Patent Application Nos. 2,409,795and 2,386,983, as well as in European Patent Application PublicationNos. 0 091 059 and 0 069 487, all of which describe various designs ofsuch irrigation hoses.

It is an object of this invention to provide an improved drip irrigationhose in which the rate of flow from each outlet port can be preciselypredetermined.

A further object of this invention is to provide a drip irrigation hosehaving outlet ports spaced along the hose at intervals corresponding tothe distance between the plants to be irrigated so that the water willflow directly toward each plant.

Another object of this invention is to provide a drip irrigation hose bymeans of which the rate of flow from each port is so regulated that eachplant receives substantially the same amount of water.

To this end, the hose according to the present invention comprises afirst tube constituting the primary duct and a second tube extendingaround the primary duct to form an outer covering, at least one of thetubes including at least one longitudinal groove capable of delimiting,with the other tube, a secondary duct, the first tube including inletports disposed at intervals and opening into the secondary duct orducts, and the outer covering including, disposed at intervals, outletports from the secondary duct or ducts interposed between the inletports.

Still another object of this invention is to provide an improved methodof producing drip irrigation hoses more rapidly, more reliably, andconsiderably more economically than has heretofore been possible, aswell as an installation for carrying out such a method.

To this end, in the method according to the present invention, a firsttube and a second tube are continuously formed at different locations,the first tube is brought to the formation location of the second tube,the latter is formed about the former, the first tube is perforated at alocation situated between the formation locations of the tubes, and thesecond tube is perforated at a location situated downstream from theformation locations of both tubes.

The installation according to the present invention comprises twoextruders provided with a first and a second extrusion head,respectively, and arranged to produce a first tube and a second tube,respectively, the latter surrounding the former, means for guiding thefirst tube toward the second extrusion head, means disposed between thetwo extrusion heads for perforating the first tube, and means disposeddownstream from the second extrusion head for perforating the secondtube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention will now be described in detailwith reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a length of a basic tube,

FIG. 2 is a perspective view of a length of irrigation hose utilizingthe basic tube of FIG. 1,

FIGS. 3 to 8 are partial sectional views showing various embodiments ofthe irrigation hose,

FIGS. 9 and 10 are top plan views of two embodiments of the irrigationhose, and

FIG. 11 is a diagrammatic top plan view of an extrusion installation forcarrying out the method of manufacture.

FIGS. 1 and 2 illustrate the principle of the first embodiment to bedescribed. A basic tube 1 is formed by extrusion in a conventionalextrusion head. As may be seen, the tube 1 has a cylindrical insidesurface and a series of longitudinal grooves 2 of identical rectangularcross-section distributed over its entire circumference. The grooves 2extend along the entire length of the tube 1, parallel to thelongitudinal axis thereof. At intervals along the bottom of each groove2 there are inlet ports 3 staggered from one groove to the next by adistance corresponding to the spacing between the plants to beirrigated. The various inlet ports 3 are thus disposed along a linespiralling around the tube 1. The pitch of this spiral corresponds tothe distance between two inlet ports 3 in the same groove 2. If n is thenumber of grooves around the circumference of the basic tube and m isthe distance between two adjacent plants, the distance between two inletports 3 in the same groove will be n×m.

As shown in FIG. 2, the irrigation hose is finished by disposing aroundthe basic tube 1 an outer covering 4, also formed by extrusion over thebasic tube 1 after perforating of the inlet ports 3. In the embodimentshown, the outer covering 4 is a cylindrical covering of uniformthickness which is joined, virtually by fusion at the moment of theextrusion, to the ribs of the tube 1 which separate the grooves 2. Asmay also be seen in FIG. 2, outlet ports 5 are contrived in the outercovering 4. In the embodiment illustrated, each of the outlet ports 5 issituated at a certain distance, predetermined and constant for all theoutlet ports, from one of the inlet ports 3 situated in the same groove2. Hence there is the same spacing between the successive outlet ports 5as between the inlet ports 3, this spacing being equal to the distancem, for example, and it will be seen that in each longitudinal strip ofthe outer covering 4 which closes one of the grooves 2, there are outletports 5 spaced by a distance equal to n×m. The water circulating withinthe primary duct will therefore enter through the ports 3 into thesecondary ducts consisting of the different grooves 2 and, after havingflowed a certain way corresponding to a certain fraction of the distancen×m, will arrive at the nearest outlet port 5 situated in the samesecondary duct and there exit to water a plant.

The important point in the dimensioning of the hose is that thecross-section and length of each secondary duct can be determined bymeans of absolutely conventional calculations as a function of the waterpressure in the primary duct and the desired rate of flow. The proposedirrigation system makes use of the fact that the flow into the secondaryducts will be laminar, so that the loss of head may be calculated interms of the hydraulic diameter of the secondary duct and of its length.For the cross-section of a secondary duct, there exists a lower limitgoverned by the type of operation, i.e., the quality of the water usedand its degree of pollution, particularly its algae content. Thecross-section of the secondary ducts being thus determined, it ispossible to calculate the length necessary for obtaining the desiredflow through the outlet port. In other words, the flow is not regulatedby either the size of the outlet ports nor by that of the inlet ports,so that these ports may be made large enough to avoid any risk of theirbeing clogged by the impurities which may be carried along. Thiscircumstance also facilitates manufacture, as will be seen below.

Returning to the calculation of flow, it will be noted that the maximumlength of a secondary duct is subject to a limit which is a function ofthe distance n×m. For if the hose is provided with n secondary ducts,every nth plant will be supplied by the same secondary duct, and thedistance between two successive outlet ports of the same secondary ductwill be n×m. For example, if the distance m between two plants is 0.8meters and the number n of secondary ducts is 10, the distance betweentwo successive outlet ports in the same secondary duct will be n×m=8meters.

The distance travelled by the water in each secondary duct will be equalto a fraction f×n×m of that distance, the factor f equalling 0.5 or avalue less than that limit.

FIGS. 3 to 8 show different forms of a basic tube 1 provided withlongitudinal grooves 2 and completed by an outer covering 4 of uniformthickness closing the different grooves 2 toward the outside. It will beseen that in FIGS. 3, 4, and 5, the grooves are arcuate, triangular, andrectangular, respectively. In these three embodiments, the basic tube 1has a cylindrical inside surface, whereas in the embodiments of FIGS. 6,7, and 8, although there are the same arcuate, triangular, andrectangular shapes for the cross-sections of the grooves 2, the insidesurface of the basic tube 1 is complementary to the outside surface sothat the wall thickness of the tube remains uniform, which is not thecase in the embodiments of FIGS. 3, 4, and 5.

FIGS. 9 and 10, on the other hand, illustrate two other possibleembodiments as far as the ratio between the length of the secondaryducts and the distance n×m between two outlet ports is concerned. FIG. 9shows an irrigation hose 6 comprising an outer covering 7 and a basictube 8. This basic tube has a single groove 9. The inlet ports 10 aremade at intervals in the bottom of the groove 9, while outlet ports 11are likewise made opposite the groove 9 in the outer covering 7. Thedistance between two successive ports 11 is, in this case, equal to m,i.e., to the distance between the plants, since here the number n is 1.Moreover, the distance between the ports 10 also equals m, and each port10 is placed at an equal distance between two successive ports 11. Thefactor f therefore equals 0.5.

Illustrated in FIG. 10 is an irrigation hose 12 having a basic tube 13with a single groove 14 and a cylindrical tube of uniform thickness asan outer covering 15. Outlet ports 16 are made in the outer covering 15at intervals equal to m, while the distance between successive inletports 17 is slightly more than m. In this case, during continuousmanufacture of the hose 12, care must be taken to cut it into successivesections of a predetermined length, as is seen in FIG. 10. This drawingfigure shows a hose with the proportions greatly exaggerated; but itwill be noted that at the inlet end of the hose, the secondary ducts arerelatively long and gradually become shorter until their length isvirtually nil at the outlet end. In other words, the factor f whichdetermines the length of the secondary ducts gradually decreases fromthe inlet end of the hose to the outlet end. Thus, assuming that thetotal length of the finished hose is known, it is clear that the lossesof head in the primary duct can be taken into account during manufacturein order to ensure a totally constant flow at the various outlet ports16. The gradually increasing loss of head in the primary duct iscompensated for by the shortening of the secondary ducts, obtained inthis embodiment in that the inlet ports 17 of each secondary ductgradually approach the corresponding outlet ports 16.

It will also be noted that in other embodiments (not shown), thealignment of the grooves 2, 9, or 13, instead of being straight andparallel to the generatrices of the hose, might equally well run along aspiral, so that all the outlet ports would be disposed along the samegeneratrix instead of being distributed along a spiral as in FIG. 2.

An irrigation hose such as described above may be produced by extrusionby means of an installation comprising, in principle, the elements shownin FIG. 11. A first extruder 18 of a conventional type is driven by amotor 19 and feeds an extrusion head 20 yielding a basic tube 21.Disposed downstream from the extrusion head 20 is a perforatingarrangement 22 which may, for example, comprise heated pins controlledso as to move radially and produce the inlet ports 3 in the bottom ofthe grooves 2 in the tube 21. Such pins may be controlled by anysuitable means, which need not be described in detail here. As statedabove, the dimensions of the inlet ports need not necessarily be veryprecise, so that the design of the perforating arrangement 22 poses noparticular problem. For instance, the ports may be produced by drillingor by milling, by sawing or by punching. A cold tool or a hot tool maybe used. The ports may be made while the material is still soft, i.e.,as it leaves the extrusion head. As a variation, however, the portsmight equally well be made after the material has cooled. If need be, avat may be placed between the head 20 and the perforating arrangement22.

A second extruder 23 feeds a second extrusion head 24 which forms anouter covering 25 on the basic tube 21 passing through it. A secondperforating arrangement 26 is disposed after the extrusion head 24 andforms at the desired locations the outlet ports 5 seen in FIG. 2.Finally, in the embodiment shown in FIG. 11, the finished hose passesthrough a cooling vat 27. However, as stated above, an intermediate vatmight also be provided, either before or after the arrangement 22. Ithas been found that the basic tube may be made of reinforced PVC and theouter covering of a polyethylene, e.g., a product resistant toultraviolet rays and to wear and tear by friction and having goodmechanical strength. As for the outlet ports 5, here, too, the shape,size, and positioning are not critical. On the other hand, the outletports and the inlet ports must be synchronized, as well as the positionsof the different ports in the basic tube and in the outer covering. Whenthe grooves forming the secondary ducts run in a spiral instead ofstraight, these grooves may be formed by means of a head 20 mountedrotatingly. In that case, the perforating arrangements might compriseonly one perforating tool rather than a number corresponding to thenumber of secondary ducts, as in the devices 22 and 26.

By means of the method described, it is possible to obtain simply,rapidly, and at minimum cost a very reliable drip irrigation hose givingcomplete operating satisfaction. In this design, there are nodetachable, cemented, or welded parts for limiting the rate of flow orfor pressure compensation. Limitation of the flow in each secondary ductis effected by determining the cross-section of the secondary ducts andthe distance the water must travel between an inlet port and the closestoutlet port. The distance travelled by the water is relatively greatconsidering the cross-section of the duct, so that the flow in thesecondary ducts is laminar, and the loss of head can be calculatedconventionally as a function of the dimensions. The large number ofsecondary ducts distributed over the entire circumference of the primaryduct makes possible long passages of the water. Compensation for lossesof head in the primary duct may be obtained by gradually reducing thelength of the secondary ducts, which consequently impliessynchronization of the perforating operations during manufacture.Furthermore, it must be ensured that the extruded product is cut intosections of strictly determined length.

For the manufacturing installation, an extruder with two twin screws maybe provided instead of two separate extruders. Provision may also bemade for a single extrusion head fed from two different extruders,combined with the perforating arrangement and forming the two superposedtubes in the same operation.

What is claimed is:
 1. A hose for drip or trickle irrigation, of thetype having a primary duct, at least one secondary duct of smallercross-section than said primary duct, a plurality of inlet ports forcausing the primary duct to communicate with each secondary duct, and aplurality of outlet ports for causing each secondary duct to communicatewith the outside, wherein the improvement comprises a first tubeconstituting said primary duct and a second tube disposed around saidfirst tube to form an outer covering, a plurality of longitudinalgrooves formed in one of said first tube and said second tube to formwith the other of said first and second tubes a plurality of separatenon-communicating secondary ducts circumferentially adjacent one anotherat any circumferential cross-section of the hose, a plurality of spacedinlet ports formed in the first tube and opening into said secondaryducts, and a plurality of outlet ports formed in said second tube andopening out of said secondary ducts.
 2. The irrigation hose of claim 1,wherein said first tube and said second tube are joined to one anotheron each side of each longitudinal groove for closing each secondary ductlaterally.
 3. The irrigation hose of claim 1, wherein each secondaryduct communicates with said primary duct through a plurality of saidinlet ports distributed along the said longitudinal groove, and eachsecondary duct further comprises a plurality of said oulet portsinterposed between said inlet ports.
 4. The irrigation hose of claim 3,wherein said secondary ducts are continuous over the entire length ofsaid hose and are separate from one another, each of said outlet portsbeing fed by the nearest of said inlet ports.
 5. The irrigation hose ofclaim 3, wherein said secondary ducts are parallel to the axis of saidhose, the successive inlet ports and outlet ports being distributedalong lines spiralling about said hose.
 6. The irrigation hose of claim3, wherein said secondary ducts have a spiral alignment about saidprimary duct, said outlet ports all being situated on the samegeneratrix of said hose.
 7. The irrigation hose of claim 3, wherein thedistance between each of said outlet ports and the one of said inletports nearest thereto in the same said secondary duct is the same forall of said secondary ducts and over the entire length of said hose. 8.The irrigation hose of claim 3, wherein the distance between each ofsaid outlet ports and the one of said inlet ports nearest thereto in thesame said secondary duct gradually decreases along said hose as afunction of the loss of head in said primary duct.
 9. The irrigationhose of claim 3, wherein said secondary ducts are formed by a pluralityof longitudinal grooves of identical cross-section contrived in theoutside surface of said first tube, the inside and outside surfaces ofsaid second tube being cylindrical and coaxial.